This research investigates a fundamental aspect of language understanding, namely, the way people construct and use mental models of situations being described in discourse. The mental model is like an internal "theater stage" that a reader or listener constructs in imagination to represent the locations, objects, characters, actions, and causal mechanisms described in a text. Readers/listeners use their developing model to interpret later statements in a discourse, to resolve ambiguities and references, to direct inferences, to learn new information, and understand how it fits into their prior knowledge. Imparting an accurate situational model is typically the main goal of instructional discourse as well as plot-centered narratives. When describing a mechanism, scene, or narrative, writers use various linguistic devices to foreground certain concepts and referents, thus placing them in the focus of attention within the reader's situational model. This attentional focusing importantly influences the way comprehension proceeds. Research has shown that memory representations of objects in focus within the mental model become highly activated, thus facilitating later references to them or retrieval of information about them. Furthermore, activation of memory objects occurs according to their proximity to the focus in the mental model. The proposed research investigates the properties and consequences of this focus of attention as it is moved around within a mental model. Shifting the focus when following characters' movements leaves a trail of activation on memory-objects along that path in the model, thus enabling rapid retrieval and reference to these objects. The proposed experiments will examine the analog, imagistic nature of the mental model, varying the properties of the spatial displays, the characters' movements, and the reader's perspective on them. The theoretical issues addressed by these experiments include how mental models are maintained, updated, and manipulated in people's working memory, whether and to what extent the models have spatial-imagery properties, and how they are constructed and oriented around a particular station-point or perspective.